From the viewpoint of an influence on environment or fuel efficiency, a hybrid electric vehicle (HEV), an electric vehicle (EV), and a fuel cell vehicle has been manufactured and sold in recent days, and new models has been continuously developed. For the so-called electromotive vehicles, use of a power supply device that can be discharged and charged is essential. As the power supply device, a secondary battery like a lithium ion battery and a nickel hydrogen battery, an electric double layer capacitor, or the like is used. In particular, having high energy density and high durability against repeated charge and discharge, the lithium ion secondary battery is believed to be suitable for an electromotive vehicle and efforts are made to develop their various types. However, to apply it to a motor driving power supply of various vehicles, it is necessary to use plural secondary batteries connected in series to guarantee a large output.
However, when a battery is connected through a connection section, an output is lowered by electric resistance of the connection section. Further, a battery with a connection section is spatially disadvantageous. Specifically, output density or energy density of a battery degrades by a connection section.
For solving those problems, a bipolar secondary battery like a bipolar lithium ion secondary battery is developed. The bipolar secondary battery has an electric power generating element having plural bipolar electrodes laminated therein and intervened by an electrolyte layer or a separator, in which a positive electrode active material layer is formed on one side of a collector and a negative electrode active material layer is formed on the other side of a collector.
To guarantee higher output density, the collector used for the bipolar secondary battery is preferably made of a lightweight material having excellent conductivity. From such point of view, a collector composed of a polymer material added with conductive materials (i.e., a resin collector) is suggested to replace conventionally used metal foils. For example, in Patent Literature 1, a resin collector composed of a polymer material in which metal particles or carbon particles are added as a conductive material is disclosed.